A storm is approaching.
Still working this out, but the key concepts are in place.
I could probably use a helpful quick-start pointer or two in using ffmpeg.
(but DAMN it is FAST! :O )
60 frames at 15 fps rendered in qtpov on Linux Mint 18.3
ffmpeg -y -r 15 -i SpiralWarp%02d.png -crf 15 -c:v libx264 -pix_fmt yuv420p
-metadata title="Prototype Spiral Warp - Bald Eagle 2018-07-22" Warp.mp4
looked good in konqeror

That is really cool, a great starting point for some interesting animated
effects. I'm following this with great interest (thinking about what the
addition of *more* spirals/vortices would look like as they all interact-- and
with some warp{turbulence...} thrown into the mix.)
As-is, it looks like the effect is 'confined' to a square; it would be great to
see it confined to a circle instead (if possible)-- to be more like a storm.